The field of the present invention is fuel rails for internal combustion engines and, in particular, fuel rails for spark-ignited, reciprocating piston internal combustion engines.
During the past three decades, a major technological effort has taken place to increase the fuel efficiency of automotive vehicles. One technical trend to improve fuel efficiency has been to reduce the overall weight of the vehicle. A second trend has been to improve the aerodynamic design of a vehicle to lower aerodynamic drag. Another trend to increase fuel efficiency is to address the overall fuel efficiency of the engine.
Prior to 1970, the majority of production vehicles with a reciprocating piston gasoline engine had a carburetor fuel supply system. In the carburetor fuel supply system, gasoline is delivered via the engine throttle body and is therefore mixed with the incoming air. Accordingly, the amount of fuel delivered to any one cylinder is a function of the incoming air delivered to a given cylinder. Airflow into a cylinder is affected by many variables including the flow dynamics of the intake manifold and the flow dynamics of the exhaust system.
To increase fuel efficiency and to better control exhaust emissions, many vehicle manufacturers went to port fuel injector systems, which replaced the carburetor with fuel injectors that injected the fuel into a port which typically served a plurality of cylinders.
Although port fuel injection is an improvement over the carburetor fuel supply system, in a step to further enhance fuel delivery, many spark-ignited gasoline engines have gone to a system wherein a fuel injector is supplied for each individual cylinder. The fuel injectors receive fuel from a fuel rail, which is typically connected to all or half of the fuel injectors on one bank of an engine. In-line 4, 5 and 6 cylinder engines typically have one bank. V-block type engines have two banks.
One critical aspect of a fuel rail application is the delivery of a precise amount of fuel at a precise pressure. In an actual application, the fuel is delivered to the rail from the fuel pump in the vehicle fuel tank. In an engine-off condition, the pressure within the fuel rail is typically 45 to 60 psi. When the engine is started, an injector firing momentarily depletes the fuel locally in the fuel rail and then the sudden closing of the injector creates a pressure pulse back into the fuel rail.
The opening and closing of the injectors creates pressure pulsations up and down the fuel rail, creating an undesirable condition wherein the pressure locally at a given injector may be higher or lower than the injector is ordinarily calibrated to. If the pressure adjacent to the injector within the fuel rail is outside a given calibrated range, then the fuel delivered upon the next opening of the fuel injector may be higher or lower than what is desired.
Fuel pulsations are also undesirable in that they can generate undesired noise. The pressure pulsations can be exaggerated in many fuel delivery systems wherein a returnless delivery system is utilized where there is a single feed into the fuel rail and the fuel rail has a closed end point. To reduce undesired pulsations within the fuel rails, many fuel rails are provided with pressure pulsation dampers.
Most dampers utilize diaphragms. Most dampers are separate components that are added to the fuel rail as a final assembly step. Most prior dampers utilized an O-ring or gasket as the primary seal. The seals created an additional leak path to the fuel rail and have been problematic. Attempts to add dampers without an O-ring seal after the fuel rail is fabricated (assembled, brazed and leak tested), requires the use of capital intensive equipment such as laser welding or induction brazing.
Some of the requirements for laser welding or induction brazing can be eliminated if the damper is added to the fuel rail before the brazing operation. However, the brazing operation traditionally produces an amount of heat that can often damage the O-ring or gasket, which in many instances, are fabricated from an elastomeric material. The heat from the brazing operation can additionally build up pressure inside the metal damper and cause bursting.
It is desirable to provide a fuel rail with a pulsation damper which eliminates the requirement for utilization of O-rings or gaskets, especially polymeric O-rings or gaskets. It is also desirable to provide a fuel rail that can have the damper added before the fuel rail undergoes final assembly and is brazed and leak tested.
The present invention provides a fuel rail which incorporates the damper into the fuel rail during the normal manufacturing process. The damper consists of two chambers which are separated by a diaphragm. The damper can be a separate part that is tacked on and finally brazed on into position or an integral feature of the main body of the fuel rail. The fuel rail can be leak tested to guarantee its integrity and the damper may be activated by pressurizing it and capturing pressurized gas or air through a simple induction welding process or by utilization of a mechanical plug. In the event the diaphragm ruptures, a cup of the damper acts as a secondary sealing chamber to stop any external leakage of fuel from the fuel rail.
Other features and advantages of the present invention will become more apparent to those skilled in the art after a review of the invention as it is explained in the accompanying detailed description and drawings.